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ls1 nova
10-04-2009, 03:12 PM
I have a small block chevy with an edelbrock MPFI system. The engine runs pretty normal but with some hesitation. If I prime the rails by turning the ignition pressure quickly drops to zero. Also drops imediately after turning truck off. What is the best way to troubleshoot the regulator, pump, injectors? Thanks
megaladon6
10-04-2009, 03:28 PM
it sounds like you're missing a check valve. maybe get pressure in the system, then clamp the supply line and see if the pressure holds when you turn the ignition off.
ls1 nova
10-05-2009, 03:23 PM
Took some pressure readings today. Key on=26psi until the pump times out the it immediately goes to zero. Running=26psi. Edelbrock recommends 42-44 with key on and i think 36 running.
camcojb
10-05-2009, 04:47 PM
Took some pressure readings today. Key on=26psi until the pump times out the it immediately goes to zero. Running=26psi. Edelbrock recommends 42-44 with key on and i think 36 running.
if the tune is set for 42-44 psi then having it lower will definitely lean it out. Not holding pressure is not necessarily a problem, none of mine hold pressure either, unless your fuel system is designed to hold pressure in the lines. If you have an adjustable regulator it needs to be adjusted with the engine idling. If it's a pre-set regulator it sounds like the pump is going away or there is a restriction in the pickup, filter, etc.; Also check pump voltage as if that drops the pump slows down, pressure goes down.

Jody
ls1 nova
10-06-2009, 07:12 PM
Thanks for all the help. Dropped the tank tonight to find one of the hose clamps loose on the pump and the check valve broke. Anybody have any input on the ac delco ep381 pump. Edelbrock sent me a walbro and I wasn't overly impressed.
Ollie8974
10-07-2009, 08:04 AM
Read below post.

https://www.pro-touring.com/forum/showthread.php?t=60626
ls1 nova
10-07-2009, 07:15 PM
That's Funny. Exactly what I did. AC delco ep381(25163473) pump from a vortec truck. Fit perfect unlike the POS edelbrock sells. Check valve blew out and got jammed in the sender. Truck runs like a dream now! I am wondering how much more I can gain with a new tune seeing how I am using the supplied edelbrock emissions legal chip. Very happy with the performance none the less.